Nitrogen oxides (NOx) are a combination of nitric oxide (NO) and nitrogen dioxide (NO2) and are a natural byproduct in the combustion of all fossil fuels. NOx is formed when the nitrogen in the air chemically interacts with oxygen released by the combustion process.
NOx has several deleterious effects. In either its pure chemical or particulate form, NOx is known to present a severe health hazard to the respiratory system. In addition, NOx is the basis for acid rain, which can affect the quality of air, soil, and water and can chemically decompose man-made structures including roads, bridges and buildings.
High voltage electron beams (500,000 to 1,000,000 Volts) have been demonstrated to remove up to 90% of the NOx emissions from a coal fired power plant. See “Accelerators for Americas Future,” Symposium Proceedings, Walter Henning and Charles Shank Chairs. Published by US Department of Energy, June 2010.
The process for removing NOx from exhaust gas with electron beams, also called “flue gas”, has been established using a catalytic process in which ammonia and water are injected into the flue gas before the gas is irradiated by a continuous electron beam. The electron beam dissociates the water molecules into free radicals, which then reacts with the NOx to produce nitric acid. The acid is neutralized by the ammonia to produce ammonium nitrate [NH4NO3], which can be used as a fertilizer. See R. Kikuchi and Y. Pelovski, “Low-dose irradiation by electron beam for the treatment of high-SOx flue gas on a semi-pilot scale—Consideration of by-product quality and approach to clean technology,” Process Safety and Environment 87 (2009) 135-143; see also U.S. Pat. No. 5,695,616 to Helfrich et al.
This catalytic process has been demonstrated in pilot coal plants in the US, Japan, Germany, Poland, China, and Russia, see S. Korenev and R. Johnson, “Electron accelerators for cleaning flue gases and for oil liquefaction,” Proceedings of EPAC08, Genoa, Italy 2008. Paper TUPP141, as well as on oil based plants, see A. A. Basfar, O. I. Fageeha, N. Kunnummal, A. G. Chmielewski, J. Licki, A. Pawelec, Z. Zimek, and J. Warych, “A review on electron beam flue gas treatment (EBFGT) as a multicomponent air pollution control technology,” NUKLEONIKA 2010; 55(3):271-277.
However, this method has not been widely adopted, because the cost of fielding the continuous electron beam source can make the process prohibitively expensive, and the need to add ammonia to the flue gas, to remove the fertilizer by-product, and to find a practical use for the fertilizer by-product produced can make the process unduly cumbersome.